The document discusses JIT-aware programming for ActionScript virtual machines. It provides examples of how different programming patterns can affect JIT compilation results. Specifically, it shows how using classes, methods, and types can influence optimization of JIT outputs. The author encourages programmers to be mindful of these language features in order to better facilitate JIT compilation and potentially improve performance.

1. 猿を
木から
落とさない
JIT-Aware AVM+ Programming
2007/03/23
omo <omo@dodgson.org>
http://www.dodgson.org/omo/

2. Tamarin↓ (w/ JIT)
SpiderMonkey↑ (w/o JIT)
http://flickr.com/photos/andrewn/125332736/
http://flickr.com/photos/subindie/336599998/

3. JIT 結果を確認する
# avmplus_sd.exe -Dverbose Hello.abc

4. JIT 0/2 package {
...
AS→ABC public class Hello {
prototype.hello
= function() {
System.write(quot;Helloquot;);
};
...
}
}
var h = new Hello();
h.hello();
...
0:findpropstrict {...}::System
2:getproperty {...}::System
4:pushstring quot;Helloquot;
6:callproperty {...}::write 1
9:pop
10:returnvoid
...

5. JIT 1/2 verify <function> ()
...
0:findpropstrict {...}::System
ABC→MIR
@25 imm 13782760
@26 imm 14133232
@27 cmop MethodEnv::finddefNsset (@3, @26, @25)
2:getproperty {...}::System
@29 ld 60(@27)
4:pushstring quot;Byequot;
@30 imm 14150032
6:callproperty {...}::write 1
@31 ucmp @29 @11
@32 jeq @31 -> 0
@33 st 13490120(0) <- @3
@34 ldop 4(@3)
@35 ldop 24(@34)
@36 lea 8(@35)
@37 st 13489476(0) <- @36
@38 ldop 40(@29)
@39 ldop 108(@38)
@40 alloc 4
@41 st 0(@40) <- @29
@42 st 4(@40) <- @30
@43 lea 12(@39)
@44 lea 0(@40)
save state:
@45 def @29
@46 def @30
@47 ci @43 (@39, @14, @44, @-1)
9:pop
10:returnvoid
...

6. JIT 2/2 generate <function> ()
...
@8 alloc 48
MIR→x86 @9 ldop 0(@5)
03D800E5 mov eax, 16(ebp)
03D800E8 mov ecx, 0(eax)
...
@40 alloc 8
@41 st 0(@40) <- @29
03D80156 mov -72(ebp), eax
@42 st 4(@40) <- @30
03D80159 mov -68(ebp), 14150032
@43 lea 12(@39)
@44 lea 0(@40)
03D80160 lea edx, -72(ebp)
@45 def @29
@46 def @30
@47 ci @43 (@39, @14, @44, 0)
03D80163 push edx
03D80164 push 1
03D80166 push ecx
03D80167 call 12(ecx)
03D8016A add esp, 12
...
03D8018B leave
03D8018C ret
...

7. 本題 : JIT-Aware Programming
JIT されないところ
●
似た or 同じバイトコードで異なる JIT 結果
●

8. JIT されないところ
●
似た or 同じバイトコードで異なる JIT 結果
●

9. JIT されないところ
package {
...
public class Hello {
// Hello$cinit
prototype.hello
= function() {
System.write(quot;Helloquot;);
};
...
}
}
// global$init
var h = new Hello();
h.hello();

10. JIT されないところ
●
似た or 同じバイトコードで異なる JIT 結果
●
例題 :
➢
メソッド呼び出し w/ メソッド定義いろいろ

11. メソッド w/ property
...
function Hello1() {
this.hello = function()
{ System.write(quot;Helloquot;); };
}
function greeting(h) {
h.hello();
}
greeting(new Hello1());
...
0:getlocal1
1:callproperty {...}::hello 0 4 ABC Ins.
4:pop
5:returnvoid
...

12. メソッド w/ property
...
0:getlocal1
@37 use @29 [1]
1:callproperty {public,Hello1.as$1,avmplus}::hello 0
@38 def @37
@39 cm MethodEnv::nullcheck (@3, @37)
...
@56 ldop 12(@42)
@57 cmop Toplevel::toVTable (@56, @53)
...
@61 cm Toplevel::callproperty (@56, ...)
4:pop
5:returnvoid
...
@66 ret @18
MIR 命令 : 約 66
ランタイム呼出 : 3

13. メソッド w/ type
...
dynamic public class Hello2 {
public function Hello2() {
this.hello = function() { System.write(quot;Helloquot;); };
}
public static function greeting(h:Hello2)
: void {
h.hello();
}
}
...
...
0:getlocal0
1:pushscope
6 ABC Ins.
2:getlocal1
3:callproperty {...}::hello 0
6:pop
7:returnvoid
...

14. メソッド w/ type
...
0:getlocal0
@33 use @17 [0]
1:pushscope
2:getlocal1
@34 use @22 [1]
3:callproperty {...}::hello 0
...
@61 cm Toplevel::callproperty (@54, @50, ...)
6:pop
7:returnvoid
...; error handling follows ...
@66 ret @11
...
@68 cm MethodEnv::npe (@3); null-pointer exception
...
MIR 命令 : 約 61 (Hello1 - 5)
ランタイム呼出 : 1(Hello1 - 2)

15. Toplevel::callproperty()
Atom Toplevel::callproperty(...) {
Binding b = getBinding(...); // ハッシュ検索
switch (b&7) {
case BIND_METHOD:
...
default:
...
return AvmCore::atomToScriptObject(base)->callProperty(...);
...
}
Atom ScriptObject::callProperty(...) {
...
Atom method = getMultinameProperty(multiname); // ハッシュ検索
...
return toplevel->op_call(method, argc, argv);
}
2 回ハッシュをひく！

16. メソッド w/ 1 -class method
st
...
public class Hello3 {
public function hello() : void
{ System.write(quot;Helloquot;); }
public static function greeting(h:Hello3)
: void {
h.hello();
}
}
...
...
0:getlocal0
1:pushscope
6 ABC Ins.
2:getlocal1
(== Hello2)
3:callproperty {...}::hello 0
6:pop
7:returnvoid
...

17. メソッド w/ 1 -class method st
...
0:getlocal0
@33 use @17 [0]
1:pushscope
2:getlocal1
@34 use @22 [1]
3:callproperty {...}::hello 0
...
@35 ucmp @34 @12
...
@47 ci @41 (@38, @12, @42, @-1); call indirect
6:pop
7:returnvoid
... ; error handling follows ...
@51 ret @11
...
@53 cm MethodEnv::npe (@3)
...
MIR 命令 : 約 53 (Hello2 - 8)
ランタイム呼出 : 0 (Hello2 - 1)

18. 仕組み : アーリーバインド
per-class
Traits
ScriptObject VTable
...
method size
slot size
traits
...
GC, etc
...
methods...
code
vtable
delegate Another Object
instances
GCHashtable
“foo”
slots...
Another Object
...
Another Object

19. まとめ : JIT-Aware Programming
一見同じバイトコードでも JIT 結果は色々
●
型やアーリーバインドを意識する
●
（ type, method, slot ）
JIT 結果をのぞく
●
速度計測を忘れずに
●
（今回やってないけど。）

20. Happy JIT-ing!
おしまい